1. Field of the Invention
This invention relates to filters having thin, flexible filtering elements, and more particularly to bag-type filters having support surfaces for maintaining the shape of the filter bag during operating conditions.
2. Description of the Prior Art
Filter assemblies using bag like filtering elements have long been useful and widely accepted. Much effort has been expended in attempting to increase the efficiency and effectiveness of these devices. Much effort has been directed towards improving the area of filtering surface that can be provided by bag filters in relation to the size of the filter housing. Additionally, efforts have been directed to adequately seal the filter housing inlet from the filtering housing outlet to prevent any escape of the material being processed, and to separate the unfiltered from the filtered material. Examples of such efforts are shown in numerous patents. For example, U.S. Pat. No. 2,591,382, issued to A. E. Smith, shows a vacuum cleaner having two separate filtering bags in an attempt to maximize the filtering efficiency. The outer bag is a cloth bag whereas the inner bag that filters the majority of the air-stream is a paper bag which would be disposable.
U.S. Pat. No. 3,771,664, issued to Schrink et al., shows a bag-type filter in a housing in which the bag has a seal at the open end which seal is compressed between the housing and the cover to seal the unit. This patent and U.S. Pat. No. 948,082, issued to Wickwire, both show basically bag-type filters having a support screen in which the bag forms a straight cylindrical surface of a single pass to act as the filter.
U.S. Pat. No. 2,331,332, issued to L. H. Latta, deals with the problem of inserting and removing the filter bag from the housing without damaging the bag when it contacts the support surface. This is accomplished by providing relatively smooth contacting surfaces between the support surface and the bag.
Other more complex bag-type filters have been provided. For example, Macro-Flow Filter Systems of 7 Hyde Street, Stamford, Conn., offered a fairly complex bag-type filter having a tubular filter element, open at both ends, folded upon itself. The filter assembly, however, required relatively elaborate multiple sealing arrangements to seal both open ends of the cylindrical bag-type filter.
U.S. Pat. No. 4,220,459, issued to Hammond et al., shows a bag-type filter having stiffening frames which are inserted within the bag to maintain the shape of the bag and to allow the bags to be inserted into the mounting plates.
U.S. Pat. No. 4,342,574, issued to Fetzer, deals with high temperature filters having filter cells lined with replaceable filter hose of heat resistant fabric or tissue.
U.S. Pat. No. 4,193,780, issued to Cotton, Jr., et al., deals with V-cell air filters which are supported by means of a heavy gauge wire mesh in a "V" or a series of adjacent "V" shapes to form a supporting frame for the filter bags.
Other patents dealing with general areas of filtration are U.S. Pat. No. 3,347,390, issued to Tietz et al., and U.S. Pat. No. 3,370,711, issued to Hitzelberger et al.